EDIT Nov 21 2020: This issue was solved thanks to staff member msmcleod who recommended changing from Musical to Absolute Time. I could not find this setting anywhere so I didn't try it right away. But last night when I did find the setting it worked flawlessly.
FYI- this is found in the Track inspector / Clip properties. The reason I didn't see it at first is you need to highlight the clip. Duh. If you select all ( Ctrl A ) it will globally change all clips.
I am going nuts
Are you sure it's not related to musical vs absolute time?
For example, say my project is at 120bpm and my clip is at measure 5, but set to absolute time ( 8 seconds in )
Changing the tempo to 240bpm, means my clip STILL plays at 8 seconds in, but on the time rule it's now at measure 9.